an assessor would look cool but unfornately they are more of a cave fish so they'd pick an overhang and hang there most of the time. of the ones bob posted i'd go for the purple firefish or court jester(although iirc, court jesters tend to bury themselves in sand, perfectly within reach of bane) i've seen zebra bar dartfish in person and have been less than impressed, however my first pick would be a peaceful damsel, either a YTBD(although mine was agressive towards new comers for a short period of time) a talbot damsel(supposed to be the most peaceful) or a couple orange stripe chormis(i've got one, had a pair but one jumped, quite peaceful)